Various devices and methods have been traditionally used to combat a physical condition known as Barrett's esophagus. Barrett's esophagus is the abnormal growth of intestinal type cells into the esophagus resulting from stomach acid chronically refluxing into the esophagus. Most people occasionally experience heartburn, which is the refluxing of stomach acid beyond the lower esophageal sphincter muscle and into the esophagus.
Such occasional heartburn is not harmful. Severe or frequent reflux, however, is harmful and known by the names gastroesophageal reflux disease (GERD) and chronic reflux esophagitis (also known as Chronic Acid Reflux, or CAR). About one out of every ten patients with GERD/CAR are found to have Barrett's esophagus. In patients with Barrett's esophagus, the healthy mucosal cells of the inner layer or the squamous epithelium of the esophagus are replaced with diseased or intestinal cells. It is believed that such growth is a defense mechanism of the body to avoid esophageal injury due to the acid refluxed from the stomach. Unfortunately, these mucosal tissue changes may lead to low, then high grade dysplasia, and eventually to cancer of the lower esophagus, known as adenocarcinoma.
A common method for destroying diseased esophageal tissue has been to cauterize or coagulate the unwanted tissue with a conventional ablation device. Ablation devices have developed as an alternative to other traditional means of eliminating unwanted tissue, such as cutting away the tissue, cryotherapy, and thermal therapy. Cryotherapy is the application of extreme cold to freeze and destroy diseased mucosal tissue. Thermal therapy is the application of heat to coagulate, cauterize and/or ablate diseased mucosal tissue. Sufficient raising or lowering of tissue temperature causes necrosis of the tissue. For convenience, the term ablate will be used herein to describe any and all of these thermal therapy processes. In use, these devices are placed adjacent the unwanted tissue and tissue is ablated, cauterized, coagulated, frozen, or burnt, as the case may be, by energy transmitted from or to the device.
Traditional ablation devices are used in conjunction with an endoscope. Most of these traditional devices are either a capping type or an insertion type. Capping type ablation devices fit over and around the end of the tubular portion of the endoscope. Such capping type ablation devices are often visually transparent to allow the user to see through them when they are viewed with the endoscope optics. Shortcomings of capping type devices include their large size, poor maneuverability, inaccuracy, complexity, and need to be and stay secured. Regarding their large size, at least a portion of capping type ablation devices is necessarily wider than the working end of the endoscope because such devices attach to endoscopes by fitting over and around the working end of the endoscope. Larger size, among other things, results in a more invasive procedure. Further, movement of capping type devices is limited to the movement of the endoscope. That is, normally there is no relative motion between a capping type ablation device and the endoscope with which it is used. The inaccuracy of capping type devices primarily results from the size and maneuverability. For instance, when targeting particular tissue, the larger size and lack of maneuverability lowers the likelihood that targeted tissue, and no other tissue, will be ablated. Further, capping devices require structure to attach the device to the endoscope. This attachment structure adds complexity to the device compared with devices not requiring such structure. In addition, such attachment structure is usually required to be selectively removable from the endoscope and there is the potential for the device to become displaced or completely disconnected from the endoscope during the procedure. Attachment structure designed to greatly lower the likelihood of unintentional disconnection would further increase the complexity and size of the device.
The other type of conventional ablation device, the insertion type, is inserted into the working channel of the endoscope. Traditional insertion type devices have opaque probes for ablating tissue. The probes contain the energy transferring devices with which the unwanted tissue is destroyed. A primary shortcoming of insertion type devices is the inability to view through the probes. This inability results in maneuvering difficulties and reduced accuracy in use. For instance, because the probe is not visually transparent, a user must estimate the position of the probe when positioning of the device within the patient and during the energy transmitting procedure. The requirement to estimate the position of the device during the energy transmission prevents the user from knowing whether the energy transmission has affected the targeted tissue until the tissue visible around the opaque tip has been affected. The likelihood of destroying healthy cells is greatly increased when such delayed and indirect feedback is used.
A primary challenge for battling Barrett's esophagus is to destroy targeted tissue without affecting healthy adjacent esophageal cells or muscular cells underlying the diseased and healthy tissue. Injury to the healthy underlying muscular tissue, for example, can lead to the creation of a stricture or constriction in the esophagus. Another challenge is to have a device that is relatively simple and easy to use. The conventional approaches to treating Barrett's esophagus, or other diseases requiring the precise and relatively easy ablation of tissue, are insufficient in these regards. Thus, there is a need for an ablation device and method for using such a device that are accurate, minimally invasive, and relatively easy to maneuver and operate.